Fire retardant polycarbonate compositions for transparent thin-wall applications

Abstract

A flame retardant composition comprising: a polycarbonate; a branched polycarbonate comprising bisphenol carbonate units, 0.01 to 1.0 mol % of a repeating unit derived from a monomer having a pendant ester group, or a combination thereof, and repeating units derived from a branching agent based on the total moles of the composition; a linear polycarbonate comprising bisphenol carbonate units and 0.01 to 1.0 mol % of a repeating unit derived from a monomer having a pendant ester group based on the total moles of the composition; a flame retardant comprising an alkyl sulfonate, an aromatic sulfonate, an aromatic sulfone sulfonate, an aromatic organophosphorus compound, or a combination thereof, and optionally a cyclic siloxane; optionally, an additive composition; and optionally, a filler.

1 . A flame retardant composition comprising
 a polycarbonate;   a branched polycarbonate comprising bisphenol carbonate units, 0.01 to 1.0 mol % of a repeating unit derived from a monomer having a pendant ester group, or a combination thereof, and repeating units derived from a branching agent based on the total moles of the composition;   a linear polycarbonate comprising bisphenol carbonate units and 0.01 to 1.0 mol % of a repeating unit derived from a monomer having a pendant ester group based on the total moles of the composition;   a flame retardant comprising an alkyl sulfonate, an aromatic sulfonate, an aromatic sulfone sulfonate, an aromatic organophosphorus compound, or a combination thereof, and optionally a cyclic siloxane.   
     
     
         2 . The flame retardant composition of  claim 1  wherein a molded sample of the flame retardant composition has
 a notched Izod impact of greater than 500 Joules per meter squared at 23° C. at a 3.2 millimeter thickness according to ASTM D256; 
 a haze of less than 4% at 2 millimeter thickness, a haze of less than 2% at 1 millimeter thickness, or a combination thereof, each according to ASTM D1003; 
 a UL-94 flame test rating of V0 at a thickness of 1.0 millimeter, a UL-94 flame test rating of V0 at a thickness of 0.8 millimeter, or a combination thereof; 
 or a combination thereof. 
 
     
     
         3 . The flame retardant composition of  claim 1  wherein the branched polycarbonate comprises
 bisphenol carbonate units and repeating units derived from a branching agent wherein the branching agent is present in an amount effective to provide 0.01 to less than 1.43 mol % branching, 
 bisphenol carbonate units, a repeating unit derived from a monomer having a pendant ester group, and repeating units derived from a branching agent wherein the branching agent is present in an amount effective to provide 0.01-4 mol % branching, 
 or a combination thereof. 
 
     
     
         4 . The flame retardant composition of  claim 1  comprising
 20-80 wt % of the polycarbonate; 
 10-30 wt % of the branched polycarbonate; 
 5-50 wt % of the linear polycarbonate comprising repeating units derived from a bisphenol and a monomer having a pendant ester group; 
 0.01-0.5 wt % of the flame retardant comprising an alkyl sulfonate, an aromatic sulfonate, an aromatic sulfone sulfonate, or a combination thereof, and optionally a cyclic siloxane; 
 each based on the total weight of the flame retardant composition which totals 100%. 
 
     
     
         5 . The flame retardant composition of  claim 1 , wherein the monomer having the ester pendant group has the structure 
       
         
           
           
               
               
           
         
       
       wherein R is C 2 -C 15  alkyl; each of m, n, p, and q are 0 or 1; m+n=1; and p+q=1. 
     
     
         6 . The flame retardant composition of  claim 1 , wherein the monomer having the ester pendant group is a branched ester. 
     
     
         7 . The flame retardant composition of  claim 1 , wherein the polycarbonate comprises
 a homopolycarbonate,   a high heat copolycarbonate derived from a high heat bisphenol monomer and optionally a low heat bisphenol A monomer, wherein the high heat bisphenol monomer is a monomer where the corresponding homopolycarbonate of the monomer has a glass transition temperature of 155° C. or higher as determined per ASTM D3418 with a 20° C. per minute heating rate,   a poly(carbonate-siloxane), or   a combination thereof.   
     
     
         8 . The flame retardant composition of  claim 1  wherein the high heat bisphenol monomer is N-phenyl phenolphthalein bisphenol, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethyl-cyclohexane, 4,4′-(1-phenylethylidene)bisphenol, 4,4′-(3,3-dimethyl-2,2-dihydro-1H-indene-1,1-diyl)diphenol, 1,1-bis(4-hydroxyphenyl)cyclododecane, 3,8-dihydroxy-5a,10b-diphenyl-coumarano-2′,3′,2,3-coumarane, or a combination thereof. 
     
     
         9 . The flame retardant composition of  claim 1  wherein the polycarbonate comprises
 a first poly(carbonate siloxane) having a siloxane content of 10-30 wt %, based on the total weight of the first poly(carbonate siloxane), 
 a second poly(carbonate siloxane) having a siloxane content of greater than 30-70 wt %, based on the total weight of the second poly(carbonate siloxane), or 
 a combination thereof. 
 
     
     
         10 . The flame retardant composition of  claim 1  wherein the polycarbonate comprises
 a bisphenol A homopolycarbonate having a weight average molecular weight of 18,000-25,000 grams per mole; 
 a bisphenol A homopolycarbonate having a weight average molecular weight of 27,000-35,000 grams per mole; 
 or a combination thereof, 
 each as measured by gel permeation chromatography, using a crosslinked styrene-divinylbenzene column and calibrated to bisphenol A homopolycarbonate standards. 
 
     
     
         11 . The flame retardant composition of  claim 1  wherein the branching agent comprises trimellitic acid, trimellitic anhydride, trimellitic trichloride, tris-p-hydroxyphenylethane, isatin-bis-phenol, tris-phenol (1,3,5-tris((p-hydroxyphenyl)isopropyl)benzene), tris-phenol (4(4(1,1-bis(p-hydroxyphenyl)-ethyl) alpha, alpha-dimethyl benzyl)phenol), 4-chloroformyl phthalic anhydride, trimesic acid, benzophenone tetracarboxylic acid, or a combination thereof. 
     
     
         12 . The flame retardant composition of  claim 1  wherein the branched polycarbonate has an endcap derived from a phenol, an alkyl-substituted phenol, an ester-substituted phenol, a cyano-substituted phenol, a halogen substituted phenol, or a combination thereof. 
     
     
         13 . An article comprising the polycarbonate composition of  claim 1 . 
     
     
         14 . A method for forming the article according to  claim 13 , comprising molding, casting, or extruding the composition to provide the article. 
     
     
         15 . The method of  claim 14  comprising molding the article comprising:
 heating at a maximum molding temperature of 285° C. at a residence time of less than 10 minutes; 
 heating at a maximum molding temperature of 295° C. at a residence time of less than 10 minutes; and 
 heating at a maximum molding temperature of 305° C. at a residence time of less than 10 minutes.